Why did Japan attack the United States naval base at Pearl Harbor?

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Pacific War U.S. troops advancing on Tarawa, Gilbert Islands, in 1943, during World War II.

Japan attacked the United States naval base at Pearl Harbor on December 7, 1941, as a preemptive strike to neutralize the U.S. Pacific Fleet. This action was part of Japan's broader strategy to conquer Southeast Asia and the Pacific region without interference from the United States. By mid-1941, U.S. economic relations with Japan had been severed, and the U.S. was supporting China in its ongoing war with Japan since 1937. Japan viewed the U.S. Pacific Fleet as the primary obstacle to its expansionist goals. The attack was intended to cripple American naval power, allowing Japan unimpeded access to vital resources in Southeast Asia.123